Caption:
Supergranules, the network cells ("dimples") seen in the Doppler image
and movie above, have puzzled solar scientists for two and a half
decades - the pattern appears to rotate faster (a few percent) than
the gas which they are made up of! Using advanced analysis of SOHO/MDI
data, a team of scientists at Stanford University believe they have
the explanation: The Sun is doing The Wave!

When people in a stadium do the wave, nobody actually moves in the direction
of the wave - they just jump up and sit down. In the same way, individual
supergranule cells don't really move faster than the solar surface; it
is just a pattern of activity moving across the solar surface in waves,
according to Tom Duvall of Goddard Space Flight Center, stationed at
the W.W. Hansen Experimental Physics Laboratory (HEPL) at Stanford.

The artist's conception shows this
for a band of supergranules rotating faster across the Sun's surface
than other features. In reality this occurs, in a much more chaotic
manner, everywhere on the Sun's surface, but is simplified here to
highlight the phenomenon.

The scientist's conception
shows a much more realistic scenario. This sequence is based on the
analysis of the original data (noise with a power spectrum resembling
that of the observations). The underlying average motion of the gas
has been taken away - as if the camera is following the solar
rotation. If you look closely, you will see individual bright points
appear and disappear, moving in all directions; up, down, left and
right. However, seen as a whole, the changing pattern appears to move
from left to right. This illusion is generated by a random
superposition of waves that are propagating predominantly from left to
right.